This invention relates generally to fluid dispensing apparatus of the type having an orbiting spray nozzle. More particularly; the invention relates to an orbital dispensing apparatus having a robust yet flexible dispensing tube assembly.
Liquid dispensing apparatus have been designed in a variety of spray gun configurations depending on the type of material being dispensed as well as the configuration of the object or surface being sprayed. One type of dispensing apparatus is an orbiting nozzle type spray gun in which a material dispensing tube is supported for movement at a material inlet end and carries a spray nozzle at a dispensing or outlet end. The dispensing tube extends through the gun relative to a longitudinal reference axis of the gun. The nozzle end typically is journalled in an eccentric bearing. A motor is used to rotate an outer bearing race so as to impart an orbiting or nutating motion to the nozzle relative to the longitudinal axis.
In known designs, the material dispensing tube is a unitary tube that must therefore either pivot at its inlet and or otherwise flex. The pivoting option presents problems because the inlet end of the dispensing tube is also a high pressure end at the material inlet. Therefore, if the seal or tube is broken, and typically the tube pivots on the primary high pressure seal, material can flow into the motor. Although flexible tubes such as plastic can be used, such tubes are not robust and are poorly suited for high pressure applications.
Another problem with known orbiting nozzle guns is that the material being dispensed tends to coat the inside surface of the nozzle shield which is typically a shroud or skirt that surrounds the nozzle.
In known orbiting nozzle apparatus, the use of a low flexibility dispensing tube and/or a pivot region at a main seal, necessitates the use of a longer tube and gun so as to achieve sufficient displacement of the nozzle without over stressing the tube and seal. Longer guns are not only more expensive but also may be more difficult to use or to install into a preexisting spraying system.
It is an object of the present invention to provide an orbiting nozzle spray gun having a more robust dispensing tube. It is another object of the invention to provide a pivot mechanism for an orbiting dispensing tube that does not adversely affect a primary seal at the pivot region. Another object of the invention is to provide a convenient way to reduce or eliminate material residue on the spray gun.
The invention provides a material dispenser having a dispensing tube assembly having an outlet end with an orifice from which material is dispensed onto a surface, and an inlet end having an opening adapted to receive material from a supply during a dispensing operation; and means for imparting orbital motion to said outlet end relative to an axis; the tube assembly having a first section having the inlet end at a first end thereof, a second section having the outlet end at a first end thereof, and a third section that flexibly joins the first and second sections. In one embodiment the flexible third section includes a plurality of rings or hoops to increase hoop strength.
The invention also provides a material dispenser of the orbiting nozzle type in which high pressure fluid seals are static and not adversely affected by the orbiting motion of the dispensing nozzle.
The use of a flexible yet robust dispensing tube permits a dispenser to be realized that is shorter but capable of providing a wide range of spray pattern dimensions without unduly stressing the moving tube assembly.
In accordance with another aspect of the invention, a shield liner is used to prevent excessive accumulation of the dispensed material on the gun components. Still a further aspect of the invention provides an air wash feature that uses pressurized air to reduce the amount of dispensed material from coating parts of the gun.
These and other aspects and advantages of the invention will be readily understood and appreciated from the following detailed description of one or more embodiments of the invention with reference to the accompanying Figures.